U.S. Pat. Nos. 5,138,227 and 5,142,195 disclose such capped high-pressure discharge lamps for optical applications. They comprise as sole bulb a high-power discharge vessel which is capped at two ends and is provided with two mutually opposite pinches. The connection between the two electrodes and the associated caps is performed via foils which are embedded in the pinches, and via supply leads which project at the end of the pinches. They are normally made from molybdenum. The supply leads are connected to electric contacts in the caps. The caps are connected to the ends of the pinches by means of capping cement. The temperature at the ends of these pinches is approximately 330 to 350.degree. C. in the installed state. At such high temperatures, which cause a high reactivity, it is disadvantageous that before baking the capping cement can run into the capillary forming between the supply lead and pinch end. Because of the high coefficient of thermal expansion of the capping cement, the thermal alternating load can cause the cement to burst the pinch. This leads to a reduced service life for the lamp.
Lamps having seals are previously known from EP-A 649164, for example.